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world and key=?

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svn: r11293
This commit is contained in:
Matthias Felleisen 2008-08-16 15:24:58 +00:00
parent a8407bdfb6
commit 729fe8a286
1 changed files with 5 additions and 5 deletions
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10
collects/teachpack/htdp/scribblings/world.scrbl
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@ -129,7 +129,7 @@ A @tech{KeyEvent} represents key board events, e.g., keys pressed or
@defproc[(key-event? [x any]) boolean?]{
is @scheme[x] a @tech{KeyEvent}}
@defproc[(ke=? [x key-event?][y key-event?]) boolean?]{
@defproc[(key=? [x key-event?][y key-event?]) boolean?]{
compares two @tech{KeyEvent} for equality}
@defproc[(on-key-event [change (-> (unsyntax @tech{World}) key-event? (unsyntax @tech{World}))]) true]{
@ -143,11 +143,11 @@ A @tech{KeyEvent} represents key board events, e.g., keys pressed or
(schemeblock
(define (change w a-key-event)
(cond
[(ke=? a-key-event 'left) (world-go w -DELTA)]
[(ke=? a-key-event 'right) (world-go w +DELTA)]
[(key=? a-key-event 'left) (world-go w -DELTA)]
[(key=? a-key-event 'right) (world-go w +DELTA)]
[(char? a-key-event) w] ;; to demonstrate order-free checking
[(ke=? a-key-event 'up) (world-go w -DELTA)]
[(ke=? a-key-event 'down) (world-go w +DELTA)]
[(key=? a-key-event 'up) (world-go w -DELTA)]
[(key=? a-key-event 'down) (world-go w +DELTA)]
[else w]))
))